FIELD OF INVENTION

This invention relates to a metal organic framework adsorbent for removing contaminants from petroleum fluid.

BACKGROUND OF INVENTION

In oil and gas exploration and production industries, chemical contamination in petroleum products obtained from drilling is a major problem to which people in this industry confront. The petroleum fluid obtained from drilling wells normally contains a mixture of gas including CO2, NO _x , So _x , water, condensate, and contaminants including mercury (Hg) and arsenic (As). These contaminants can cause many drawbacks to the operations, such as corrosion and process fouling. Accordingly, there are many researches on removing CO2, and mercury Hg and As from the petroleum product in order to obtain the petroleum product with less impurities before feeding to other units.

Current methods to remove CO2 from the gas stream are based on membrane technology. However, there are still disadvantages on the applications of membranes for removing CO2 related to (1) the limitation of membrane separation performance, i.e. gas permeance and selectivity, and (2) the poor membrane stability and short lifetime when exposing it to a gas stream containing the impurities of acid gases, such as CO2, SO _x and NO _x . Thus, there are many researches seeking alternative materials with regeneratable capabilities that are suitable for removing CO2 from the gas stream.

Metal-organic framework (MOF) is a crystalline material constructed from metal- containing nodes and linkers. Combinations of properties of a metal part and organic linker part in the same structure lead to special properties such as designable porosity, internal pore surface functionality, and high surface area. This makes MOFs an interesting material for many applications including, but not limited to, adsorbents, gas storage, chemical separations, chemical sensing and catalysis, ion exchange, light harvesting, and drug delivery.

PCT publication WO 2010/000975 A1 disclosed iron carboxylate metal-organic frameworks (MOF) materials, for the separation of mixtures of molecules having different degrees and/or a different number of unsaturations with an adjustable selectivity. Each synthesized MOF materials consisted of iron ions, anions (for examples, halide, hydroxyl and R-(COO) _n ), and spacer ligands comprising radicals and carboxylate group. The disclosed MOF had a strong affinity for molecules containing at least one unsaturated group. Thus, they could be used in various separation processes, especially in hydrocarbons.

M. Maes, et. al. (J. Am. Chem. Soc. 2010, 132, 7, 2284-2292) disclosed the liquid- phase separation of the aliphatic Cs-diolefins, mono-olefins, and paraffins, using threes MOFs. All MOFs had spacious cages that were accessible via narrow cage windows with a diameter of less than 0.5 nm. The document also disclosed that the MOF [Cu3(BTC)2] (BTC = benzene-1 , 3, 5-tricarboxylate) could separate Cs-olefins from paraffins. F. Vermoortele, et. al. (J. Am. Chem. Soc. 2011 , 133, 46, 18526-18529) disclosed various metal-organic frameworks (MOFs) including [TigOs(OH)4(BDC)6], [TisOg(OH)4(BDC- NH2) _d ], and [A1 _B (OH) ₄ (OCH ₃ ) _B (BDC-NH2) ₆ ], (BDC = 1,4-benzenedicarboxylate), for adsorbing para-disubstituted alkylaromatics, such as p-xylene from an isomer mixture. Their unique structure of MOFs contains octahedral cages, which can separate molecules based on differences in packing and interaction with the pore walls, as well as smaller tetrahedral cages, which are capable of separating molecules by molecular sieving.

United States patent US 8,758,482 B2 provided a method for adsorbing or separating carbon dioxide from a mixture of gases using a porous MOF, Zn ₂ (BPDC) ₂ (BPEE).2DMF (BPDC = 4.4-biphenyldicarboxylic acid, and BPPE = 1 ,2- bis(4-pyridyl)ethylene), having a plurality of layers of two-dimensional arrays of repeating structural units, which resulted in a lower carbon dioxide content in the gas mixture. This porous MOF is solvothermally synthesized by mixing Zh ₂ GN03)·6H ₂ 0, FhBDPC, and BPEE at molar ratio of 1 : 1 : 1 in 15 mL of dimethylformamide (DMF) and heating at 165 °C. for 3 days.

However, a need exists for a material useful for removing CO2 including other contaminants such as Hg, As, and hydrogen sulfide (H2S) from the petroleum fluid obtained from the exploration and production, since none of the abovementioned documents disclosed specific MOF with a high performance in adsorbing CO2 including the other contaminants for petroleum industry. Therefore, this invention provides a MOF having a specific formula that is suitable for the removal of CO2 and other contaminants from the petroleum fluid with a high performance.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a metal-organic framework that is suitable for the removal of CO2 and other contaminants such as Hg, As, and hydrogen sulfide (H2S) from the petroleum fluid with a high performance. The metal-organic framework has a chemical formula:

— [Cu _ra (Br ₂ BDC) _n (OH) _x (DMF) _y ]—

Wherein m, n, x and y are independently selected from an integer of 1 to 5.

In another embodiment, the metal-organic framework according to the present invention is obtained from a method comprising steps of: i) mixing a salt of copper (II) (Cu ²⁺ ) and 2,5-dibromobenzene-l,4- dicarboxylic acid (H2Br2BDC), dimethylformamide (C3H7NO) and methanol (CH3OH) and water together; and

ii) heating the mixture from step i) and collecting product. wherein the mixture from step ii) is heated at temperature in the range of 70 to 110 °C. for 1 to 3 days.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 shows green plate- shaped single crystals of Sample 1.

Figure 2 shows FT-IR spectrum of Sample 1.

Figure 3 shows PXRD pattern of Sample 1.

Figure 4 shows asymmetric unit of Sample 1.

Figure 5 shows 3D framework structure of Sample 1.

Figure 6 shows Brunauer-Emmett-Teller surface area of Sample 1.

Figure 7 shows thermal stability (TGA curve) of Sample 1. Figure 8 shows mercury adsorption performance of Sample 1.

Figure 9 shows CO2 adsorption performance of Sample 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a metal organic framework (MOF) that is suitable for the removal of CO2 and other contaminants such as Hg, As, and hydrogen sulfide (H2S) from the petroleum fluid with a high performance. Details of the present invention can be elucidated according to the specification as follows.

Technical terms or scientific terms used herein have definitions as understood by those having an ordinary skill in the art, unless stated otherwise.

Equipment, apparatus, methods, or chemicals mentioned here means equipment, apparatus, processes, or chemicals commonly operated or used by those skilled in the art, unless explicitly stated otherwise that they are equipment, apparatus, methods, or chemicals specifically used in this invention.

The use of the singular or plural nouns with the term“comprising” in the claims or in the specification refers to“one” and also“one or more,”“at least one,” and“one or more than one.”

All compositions and/or processes disclosed and claimed are aimed to include aspects of the invention from actions, operation, modifications, or changing of any parameters without performing significantly different experiments from this invention, and obtaining similar objects with the same utilities and results of the present invention according to persons skilled in the art although without mention of the claims specifically. Therefore, substitution or similar objects to the present invention including minor modifications or changes which can be clearly seen by persons skilled in the art should be considered within the scope, spirit, and concept of the invention as appended claims.

Throughout this application, the term“about” is used to indicate that any value presented herein may potentially vary or deviate. Such variation or deviation may result from errors of apparatus, methods used in calculation, or from individual operator implementing apparatus or methods. These include variations or deviations caused by changes of the physical properties. Following is a detailed description of the invention without any intention to limit the scope of the invention.

According to one embodiment of the invention, the present invention provides a metal-organic framework having a chemical formula:

— [Cu _ra (Br ₂ BDC) _n (OH) _x (DMF) _y ]—

Wherein m, n, x and y are independently selected from an integer of 1 to 5.

In a preferred exemplary embodiment, the metal-organic framework having a chemical formula:

— [Cu _ra (Br ₂ BDC) _n (OH) _x (DMF) _y ]— wherein:

m is selected from an integer of 3 to 5;

n is selected from an integer of 2 to 4;

x is selected from an integer of 1 to 4; and

y is selected from an integer of 1 to 4.

In a more preferred exemplary embodiment, the metal-organic framework having a chemical formula:

— [Cu4(Br ₂ BDC) ₃ (OH)2(DMF)]— .

In another embodiment of the invention, the metal-organic framework according to the present invention is obtained from a method comprising steps of: i) mixing a salt of copper (II) (Cu ²⁺ ) and 2,5-dibromobenzene-l ,4- dicarboxylic acid (H ₂ Br ₂ BDC), dimethylformamide (C3H7NO) and methanol (CH3OH) and water together; and

ii) heating the mixture from step i) and collecting product. wherein the mixture from step ii) is heated at temperature in the range of 70 to 110 °C. for 1 to 3 days.

In another exemplary embodiment, the salt of copper is selected from copper (II) nitrate, copper (II) chloride, copper (II) sulfate, copper (II) acetate, or a mixture thereof. In a preferred exemplary embodiment, the salt of copper is copper (II) nitrate.

In another exemplary embodiment, a mole ratio of the salt of copper and 2,5- dibromobenzene-l,4-dicarboxylic acid (hhBnBDC) is 1 :1 to 2:1.

In another exemplary embodiment, a mole ratio of dimethylformamide (DMF), methanol (CH3OH) and water is 1 :1 :1 to 3 :3 : 1.

In another exemplary embodiment, in stepi), 0.015 to 0.030 mole of benzene-1 ,3,5- tricarboxylic acid (TMA) is further added into the mixture.

In a preferred exemplary embodiment, the mixture of step ii) is heated at temperature in the range of 80 to 100 °C. for 1.5 to 2.5 days.

In another exemplary embodiment, the mole ratio between the metal-organic framework according to the present invention can be used for removing mercury vapor, hydrogen sulfide, carbon dioxide gas, carbon monoxide, or the combination thereof from petroleum fluid.

In a preferred exemplary embodiment, the metal-organic framework according to the present invention can be used for removing mercury vapor, hydrogen sulfide, carbon dioxide gas, carbon monoxide, or the combination thereof from petroleum fluid by an adsorption between the petroleum fluid and the metal-organic framework.

In a more preferred exemplary embodiment, the metal-organic framework according to the present invention can be used for adsorbing mercury vapor, carbon dioxide, or the combination thereof from petroleum fluid.

Hereafter, examples of the invention are shown without any purpose to limit any scope of the invention.

Example

Chemicals

All chemicals and solvents employed were commercially purchased and used without further purification.

Synthesis of-— rCutfBrzBPC OH^fPMF)!— (Sample 1) The synthesis of Sample 1 to 4 were done under the conditions indicated in Table 1. According to Table 1, for each sample, metal and all ligands were mixed in the reactor containing a solvent mixture, and stirred at room temperature about 10 minutes. Then the reaction mixture was heated to the temperature indicated for each sample under autogenous pressure, and maintained at this temperature for about 48 hours. The heated reaction mixture was allowed to cool to room temperature. After filtration, the obtained product was washed with acetone and dried in air at room temperature.

Table 1 Synthesis condition of metal-organic framework samples

Note: BΏTR is 2,5-Dibromoterephthalic acid and TMA is benzene-1 ,3, 5 -tricarboxylic acid. From Table 1 , the result showed that Sample 1 is the optimum because it provided product in a crystalline form while the other conditions provided powder form. Thus, Sample 1 was used for the following tests. As shown in Figure 1, green plate-shaped crystals of Sample 1 were obtained in 44% yield based on Cu(II) source.

Characterization of Sample 1 Attenuated Total Reflection-F ourier Transform Infrared Spectroscopy (ATR-

FTIR) spectrum of Sample 1 was recorded in the region of 650 to 4,000 cm ¹ . As shown in Figure 2, the broad band around 3,000 to 3,700 cm ¹ was assigned to the OF! vibration of hydroxyl and carboxyl groups. The bands in the region about 750 to 875 cm ¹ were assigned to aromatic C-H out-of-plane bending vibrations, while the bands in the region about 1 ,250 to 1,490 cm ¹ corresponded to C-O stretching. The bands at 1 ,374 cm ¹ and 783 cm ¹ were assigned to the symmetric stretching of carboxylic groups in BnBDC ligand and the Cu- O stretching mode respectively.

Powder X-ray diffraction (PXRD) and single crystal X-ray diffraction (SCXRD) of Sample 1 were investigated. As shown in Figure 3, PXRD pattern of Sample 1 indicated that the bulk of Sample 1 was a highly pure crystalline product, since sharp peaks are observed from the PXRD pattern. Moreover, according to the results of SCXRD, a summary of crystal data of obtained MOF shows in Table 2. It implied that Sample 1 crystallized in the triclinic crystal with P-1 space group. The asymmetric unit of Sample 1 consists of 4 copper ions, 3 B^BDC ligands and coordinations of DMF and hydroxide molecules as shown in Figure 4. The three dimensional framework structure of Sample 1 could exhibit in Figure 5 showing a small pore size, in the range of about 0.5 to 0.8 nm, due to steric effect of Br-group. Moreover, when coordinated solvents were removed, The Cu position would be empty and can act as active site potentially suitable for chemical reaction or molecule capture.

Table 2 Crystal data of Sample 1

Surface area of the prepared Sample 1 was investigated. Sample 1 was activated by soaking in acetone at room temperature for about 7 days then heating under vacuum at about 100 °C ovemightThe testing condition was at N2 loading about 0.589 cm ³ (STP) g ¹ , at about 77 K, and about 1 bar. As shown in Figure 6, Sample 1 had the type-II sorption isotherm. The Brunauer-Emmett-Teller surface area of Sample 1 was about 119.83 m ² g ¹ and a mean pore width of Sample 1 was about 6.57 A (based on Horvath-Kawazoe mode).

Moreover, thermal stability was investigated by thermal analysis in the temperature range 25 to 1000 °C under nitrogen atmosphere. As shown in Figure 7, The first weight loss at about 100 °C corresponded to the loss of two hydroxy molecules and the loss at about 200 °C corresponded to the loss of one DMF molecules. The host framework of Sample 1 was collapsed after temperature of about 500 °C. The final residual product was possibly CuO. Mercury adsorption performance of Sample 1

Mercury adsorption capacity of Sample 1 was investigated using about 0.1 g of Sample 1 for adsorbing 30 mL of Hg ²⁺ solution at the concentrations of about 1,000, 3,000, 5,000, and 10,000 ppm respectively. As shown in Figure 8, it was found that a large quantity of Hg was adsorbed on Sample 1 rapidly (within 5 minutes). The adsorption capacity was steady after about 60 minutes.

CO2 adsorption performance of Sample 1

C02 adsorption capacity of Sample 1 was tested at Standard Temperature and Pressure (STP) condition. The result was shown in Figure 9. The CO2 adsorption capacity of Sample 1 was about 12.5 mg-g ¹ . Moreover, CO2 uptake in Sample 1 rapidly occurred at p/po about 0.2. This observation suggested that CO2 easily stayed in the MOF structure of Sample 1 due to suitable interaction created between CO2 molecule (guest) and the structure (host).

BEST MODE OF THE INVENTION Best mode of the invention is as provided in the description of the invention.